Process of finishing leather



Patented May 28, 19%

PA ENT orr ca PROCESS OF FINISHING LEATHER Leon B. Conant, Boston, Mass.

No Drawing. Application April 4, 1939, Serial-No. 265,973 I 4 Claims.

This invention relates to an improvement in the heat treatment of leather having application,

in particular, to its preparation and character immediately preceding its impregnation orper- 5 meation by liquid oleaginous material. 1 The primary purpose of this invention is to give effect to the saturation of the leather fibre by ahot oleaginous liquid filler by removing, prior. to its immersion therewith, all of the; hygroscopic tion .and pre-heating thereof. 7

The tanner and currier of leather,. is

afraid of the effect ofheat, or rather of its energy, upon leather with the result that leather,

heretofore, has never been freed of its hygroscopic water content prior toits stufling.

with fillers. Hence the leather fibres-have not haddirect contact with the impregnating'fflnishing oils; instead the liquid wax, or the oils, as ordinarily introduced, merely clog the pores and interstices of the leather. That is to say, the

tanned fibres of the leather during its currying' used in drying leather in a tannery; 212 F.has

been considered prohibitive. Yet, neitherone can effect sufflcient dehydration for anypermanent impregnation by oil. It is my purpose to employ heat. as high as 300 F. or, more or less as required, to make the leather absolutely anhydrous and hot in complete adaptation for its impregnation, preferably by heated oleaginous liquid filler applied -thereto while at approximately equal temperature with the leather itself. In my U. S. Patents Numbered 1,719,101, 1,769,943, 1,787,145, 1,934,038, and 2,032,471, each entitled Process of yulcanizing rubber to leather, I have described the dehydration and pre-heating of leather to adaptation for its union withrubber composition during hot vulcanization whereby its original character and quality are in no. way injured or impaired. Under modern methods most rubber compositions are vulcanized at 260 F. and up. 300 F. is a fair average. By the use of the patented processes aforesaid, leather is adaptable to these and to even higher 50 vulcanizing temperatures.- Hence, my experience of many years in pre-heating leather to. adaptation for the dry heat of hot vulcanization. at elevated temperatures enabled me to discoverand perfect this process of Dre-heating leather moisture in the leather by an adequate dehydra assures rapid and beneficial absorption of the' hot-oleaginous liquid. Therefore, this new process 7 effects real saturation of the leather fibres and thereby prevents the leather from cracking during wear. Ordinarily leather upperscrackbecause the oleaginous fillers are put in on top of the hygroscopic wateralready present therein. Such practice of finishing upper leather for instance, only places the oils between the moisture laden fibres. Acutally, the semi-moist fibres are not truly impregnated. Water and oil do not mix. Consequently, when shoes are-cleaned the oleaginous filler-in theuppers is washed out of the leather pores until finally 'none is left therein and the uppers crack. Accordingly this process is designed primarily to eliminate the hygroscopic water present in leather by heating the same to complete dehydration, and then-while so heated, introducing its quota of oleaginous content therewith in intimate association with the fibres thereof. It should be understood, however, that 'my preference is to impregnate the -leather with hot paramn wax blended with rubberunder heat and eventually coagulated as incorporated therein.

The basic principle of my process requires that the leather must be pre-heated to complete dehydration so that its fibres shall be absolutely free of all hygroscopic moisture when immersed in the oleaginous bath. Moreover, whatever the temperature of the bathmay be, I prefer the leather be hotter. Also, I prefer that the bath be heated well above 220 F. because the hotter the elevated temperature of the bath the quicker the impregnation of the hot leather is completed. In addition I propose,'on occasion,-to use compounded rubber composition in the hot oleaginous liquid and beside dispersing or dissolving it in the molten paraflln, to vulcanize it therewithin in the presence of sulphur and other suitable agents. Also, I plan if needed to apply heat and pressure to the impregnated leather.

In making my process effective I take leather of to suit, or, the hot oleagin'ous liquid may be kept at a sub-vulcanizing temperature while the rubber compound is dissolved therein and while the leather is being impregnated and then upon removal from the bath, the saturated leather may have the rubber cured therein with heat and pressure. When now the leather has become impregnated to suit, it is removed from the paraflinrubber bath and compressed under heat and pressure or simply allowed to dry out. When dry an improved durable and serviceable leather is at hand. It is understood that any variety of compounding may be used in blending crude rubber or rubber composition with the molten paraflln or tallow or other tat, or a combination thereof, as desired. If colored leather is being treated care must be used not to destroy its finish. Such leather should be dipped briefly. Incidentally, my pre-heating of leather to adaption helps to preserve its color. Oak tanned sole leather as heated in advance by my process may be readily treated in the hot oleaginous bath. Otherwise it would be ruined. It too should be handled so as to retain its natural color. Chrome sole leather immersed in the bath is no problem.

' fabric, leather, etc.

This process may be summarized as comprising the impregnation of hot dehydrated leather by heated oleaginous liquid.

I claim:

1. The process comprising pre-heating leather at a temperature above, 220 F. and removing all of. its hygroscopic water content and then, while so heated, impregnating it with hot oleaginous liquid.

2. The process comprising pre-heating leather at a temperature above 220 F. and eliminating all of its hygroscopic water content and then, while so heated, immersing it for impregnation in a hot oleaginous liquid heated to a lower temperature.

3. The process comprising pre-heating leather at a temperature above 220' F. and removing all of its hygroscopic water content,and then, while so heated, immersing it in a hot oleaginous bath comprising a blendof paraflln and rubber.

4. The process-comprising pre-heating leather I at a temperature above 220 F. and removing all of its hygroscopic water content and then,

- while so heated, immersing it in a hot oleaginous 

